Vernalization and Photoperiodism — 2 — A Symposium 



seed to give such grain their specific quota of low temperature in the laboratory or the 

 barn and to sow them in the spring in the hope that they would come into ear in the 

 same season, that is, they would behave like spring varieties, although not, as some have 

 erroneously stated, to the extent of being "converted" into spring varieties. 



Gassner (1918) was one of the early chillers of grain, giving cereals in the labora- 

 tory the dose of low temperature they would normally receive in the field after being 

 sown in the autumn in Germany. His work is discussed later. In subsequent years 

 others chilled various types of seeds, but the interest of agricultural physiologists be- 

 came transferred to the relations between light and development and particularly to the 

 work of Garner and Allard and their successors on the photoperiodic reactions and 

 categories of plants. 



The interest in temperature was, however, revived and the attention given to de- 

 velopmental physiology as a whole stimulated by the elaboration by Lysenko and his 

 associates at the Institute of Plant Breeding and Genetics, Odessa, of the technique 

 which has come to be known throughout the English-speaking world as vernalization. 

 This technique is considered by the Russians to differ from that of Gassner in recog- 

 nizing that only a minimum of growth is essential during low temperature exposure 

 so that development can take place. 



The theoretical principles which were elaborated from the experimental data quickly 

 exerted a revolutionary effect on the whole trend of Soviet research in plant biology, 

 expressed in a spate of scientific and agronomic articles dealing with theory and prac- 

 tical applications. 



Largely through the medium of the publications of the Imperial .Agricultural 

 Bureaux (1933, 1935), this technique and the theoretical principles were made available 

 to English-speaking readers, and this was followed by many experiments on the ver- 

 nalization of a wide range of crops under a wide range of environments. The technique 

 was regarded as the solution of the problem of bringing crops to maturity in the short 

 Northern summer and of producing crops in drought-affected regions, of bringing high 

 cash value crops such as market garden or greenhouse plants to maturity in time to 

 catch early markets, or of producing seed in one year from biennial or perennial crops 

 not normally fruiting in their first year. It must be admitted that this was a period 

 of dogmatic assertions and exaggerated or ill-founded claims, of uncertain techniques 

 and an incomplete understanding of the fundamental biological principles. That period 

 is now past and it is therefore appropriate to review its consequences, and to examine 

 the changes in scientific knowledge and agricultural or horticultural practice which have 

 been achieved. 



It will be convenient to deal with this by using a combination of the historical and 

 geographical approaches, thus indicating the international nature of the problems and 

 how investigators in many different countries have been tackling them. In the 

 U. S. S. R., where the technique of vernalization had its origin, the emphasis through- 

 out has naturally been on the applied and practical results to be obtained from its use. 

 After the "fashion" created by the I. A. B. publications had died down, the nature 

 of the interest in countries outside the U.S.S.R. has varied considerably. In Germany 

 it was primarily practical, concerned with its use in making possible the cultivation 

 of such only partially adapted crops as the soybean. Interest in India is both academic 

 and practical, the latter to the extent that centres for vernalization of crop seeds have 

 been suggested, in order to supply cultivators with properly treated seed which, when 

 sown, would produce plants which would reach maturity more rapidly than those from 

 untreated seed and thus avoid a period of adverse environment such as excessive heat, 

 drought or floods. 



In Great Britain, on the other hand, research has been concerned primarily with 

 the fundamental biological processes underlying the technique of vernalization. The 

 work of F. G. Gregory, O. N. Purvis and others of the Research Institute of Plant 

 Physiology of the Imperial College of Science and Technology, South Kensington has 

 provided an important analysis of the causal factors in this reaction to temperature treat- 

 ment. The historical trend of these experiments is reviewed later. 



Chilling of Seed : — Many reviewers have suggested that there is 

 nothing new in the vernaHzation technique. McKinney (1940) has 



